Fuse construction



March 10, 1970 A. J. TAORMINA ETAL FUSE CONSTRUCTION Filed July 26, 1967 FIG.6

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S m l Y m m N R E O V T N T HG A TI. N 08 HE? MM AM- m l F 8 6 8 7 \M) m m 0 6 6 4 6 ,2 mwv 7 "W r W/ e m m United States Patent 3,500,462 FUSE CONSTRUCTION Anthony J. Taormina, Detroit, and James T. Gregory, Garden City, Mich., assignors to Essex International, Inc., a corporation of Michigan Filed July 26, 1967, Ser. No. 656,111 Int. Cl. H01h 85/08, 815/48 US. Cl. 337-187 9 Claims ABSTRACT OF THE DISCLOSURE A fuse which also acts as a terminal connector molded from a non-conducting plastic material. The fuse is U-shaped with a bridge connecting the legs of the U. The legs and bridge of the U are plated with a layer of electrically conductive material. The size of the bridge, as well as the thickness of the plating on the bridge, determines the amperage rating of the fuse. The plating on the bridge section of the fuse melts, breaking the circuit when there is a current overload. The legs of the fuse fit into terminal receptacles and in some instances may support the terminals in position relative to one another.

BACKGROUND OF THE INVENTION This invention relates to an improved fuse construction and more particularly to a fuse construction especially suitable for automotive circuits.

The conventional, low amperage fuse construction used in automotive circuits is relatively fragile and expensive. The fusible element itself usually takes the form of a thin wire filament mounted within a transparent glass tube. The wire filament is connected to terminal caps at either end of the glass tube. Constructing such a fuse has proven to be a relatively delicate and expensive operation. Furthermore, the end product itself is fragile and easily broken.

Such fuses, if not properly constructed, may fail due to the jolting and jarring of a vehicle. An effort to overcome the failure of fuses and provide an improved automobile fuse is disclosed in US. Patent No. 2,941,059, June 14, 1960, granted to Sims et al. Sims discloses a fuse comprised of a non-conductive flat, U-shaped sheet of material with conductive material plated on the legs of the U and with a precisely dimensioned strip of conductive material plated across the flat base portion of the U connecting the legs. The conductive material is applied by printed circuit methods to the flat sheet. The rating of the fuse is controlled by accurately controlling the dimensions of the strip of plated conductive material plated on the base of the U. To fuse a circuit, the legs of the fuse are inserted in circuit terminals. When the circuit is overloaded, the flat strip of conductive material melts, breaking the circuit.

The device of Sims is a significant advance in fuse construction. It is rugged and withstands the sudden jolts frequently incurred in auto circuits. Further, the Sims device is easy to handle and replace. However, the device of Sims is difficult and costly to manufacture. That part of the fiat sheet from which conductive material is to be excluded, must be precisely masked prior to adhering conductive material onto the sheet. Also, the device of Sims is fragile in the sense that the flat sheet may accidently bend causing a hairline fracture in the strip of fuse material thereby drastically altering the characteristics of the fuse. Moreover, the device of Sims and others is bulky and requires relatively large terminal blocks and fuse clips.

SUMMARY OF THE INVENTION In a principal aspect, the present invention is a fuse comprising a pair of use terminals structurally interconnected 3,500,462 Patented Mar. 10, 1970 ice by an insulating material and electrically interconnected by a separate fuse bridge member which is completely plated with an electrically conductive material. The fuse terminals comprise a pair of rigid prongs which are inserted into terminal receptacles associated with separate wires. The fuse not only acts to break an overloaded circuit, but also in some instances it may provide a means for holding the wire terminals in an interconnecting relationship.

As a feature of the invention, a fuse and the wires connected by the fuse may be inserted and held in position in a modular mounting case which has multiple cavities for receiving pairs of used wires. The fuse may also be utilized with conventional fuse clips mounted on a fuse block.

It is thus an object of the present invention to provide an improved fuse construction.

It is a further object of the present invention to provide a more rugged yet less expensive fuse construction.

Another object of the present invention is to provide a fuse which may be utilized to hold a pair of wire terminals in an interconnected relationship.

It is a further object of the present invention to provide a fuse construction which insures connection of the proper pairs of wires with one another while fusing the circuit created by those wires.

Still another object of the present invention is to provide a means for mounting multiple fused pairs of wires adjacent one another for ease of access and replacement of fuses.

One further object of the present invention is to provide a relatively smaller and compact fuse assembly at a lower cost.

These and other objects, advantages and features of the present invention will be set forth in greater detail in the drawings and detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 illustrates the molded fuse body and the initial steps of fabricating the fuse;

FIGURE 2 shows the fuse body of FIG. 1 after a layer of fuse metal has been plated thereon;

FIGURE 3 shows the fuse of FIG. 1 inserted in a pair of terminal blocks;

FIGURE 4 illustrates a series of fuses inserted in stacked terminal blocks and a cross section of the interconnection of a fuse and a terminal block;

FIGURE 5 shows alternative terminal block constructions;

FIGURE 6 illustrates an alternative fused terminal block construction inserted in a mounting case;

FIGURE 7 is a plan view illustrating the terminal block and fuse mounted in the modular mounting case as shown in FIG. 6; and

FIGURE 8 illustrates an alternative construction of the fuse in combination with a fuse clip board.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates the initial steps in the process of making the improved fuse construction 10. A fuse body member 10 is preferably cast or molded froman electrically non-conducting, thermosetting, plastic material, such as phenolic. Thermoplastic materials are also suitable. The main body portion 11 is U-shaped to form substantially parallel prongs 12 and 1-4. A strut or bridge 16 connects the prongs 12 and 14. The strut is preferably of cylindrical cross-section with a constant diameter. Likewise,

the main body portion 11 preferably has a constant diameter, cylindrical cross-section.

FIG. 2 illustrates the final steps in the construction of the improved fuse. The main body portion 11 is partially plated by an electrically conductive material 18. The conductive material 18 is plated only on the legs 12 and 14 and completely around the bridge member 16, for example, by dipping the body member 10 in a bath of conductive material. A suitable plating material is it cdompound containing by weight 63% tin and 37% By increasing the thickness of the plating, the amperage rating of the fuse is increased. For example, a fuse with a 63/37 tin-lead plating thickness of 0.001 inch on an 0.032 inch constant diameter and 0.103 inch long bridge member 16 has a 3 amp rating. An increase in plating thickness to .002 inch produces a 6 amp fuse, an 0.004 inch thickness produces a 7.5 amp fuse, an 0.006 inch thickness produces a 12 amp fuse, and a 0.010 plate thickness produces a 15 amp fuse. These ratings are approximations for a fuse of the above dimensions. Variations result depending upon the fuse metal used and the dimensions of the bridge member 16.

It is important to note that the configuration of the bridge member 16 may be altered while the plating thickness remains constant in order to vary the amperage rating of the fuse. Thus a bridge member 16 may be cast in various diameter sizes and/or shapes according to the fuse characteristics desired by the fabricator. The length of the bridge 16 is not a critical factor and may be varied without any appreciable effect on the current rating.

FIG. 3 illustrates the combination of a fuse 10 of the type shown in FIG. 2 with a pair of terminal blocks 36 and 38. The blocks 36 and 38 are formed from an insulating material, preferably an extruded plastic. The prongs 12 and 14 of the fuse 10 are mated with terminal receptacles (not shown in FIG. 4) in the blocks 36 and 38 respectively. The terminal receptacles in the blocks 36 and 38 are in turn electrically connected with the lead wires 40 and 42 respectively. The fuse serves to break the circuit when the current passing through the wires 40 and 42 overheats the metal on the bridge 16. A strap or support (not shown) may be used to hold the terminal blocks 36 and 38 rigidly in position in respect to one another.

FIG. 4 illustrates the terminal connecting means or terminal connector 50 within the terminal block 44. The terminal block is generally of a rectangular cross section with a hollowed out cylindrical center portion 46. The lead wire 48 is inserted into the hollow portion 46 and fastened to the terminal connector 50. The opposite end of the terminal connector 50 is a receptacle 51 adapted to slidably receive a prong either 12 or 14. Each terminal block 44, 45 and 47 is similarly constucted. Thus when pairs of blocks (for example, 40 and 42 in FIG. 4) are properly positioned on a circuit board, for example, electrical connection may be secured by the fuse 10.

FIG. 4 shows a number of fuses 10 connecting pairs of terminal blocks 44, 45 and 47. The pairs of connected blocks 44, 45 and 47 may be fastened together as a unit and mounted as a unit under the dashboard of an automobile. n the other hand, the blocks 44, 45 and 47 may be integrally cast and the wires and fuses 10 inserted into the proper openings in the blocks.

FIG. illustrates a construction of the terminal blocks which promotes proper matching and fusing of separate wires in a separate terminal block. Blocks 52 and 54 are molded or extruded with adjacent sides 56 and 58 designed to mate. A fuse (not shown) interconnecting the terminal receptacles 60 and 62 within the terminal blocks 52 and 54 respectively cannot be inserted into the receptacles 60 and 62 unless the blocks 52 and 54 are properly mated. In a similar manner the side 64 of the block 70 is molded to mate with the side 66 of the block 68.

A further modification is illustrated in the blocks 68 and 70. Slots 72 in block 70 and 74 in block 68, are

molded to receive the bridge 16 of the fuse 10. Thus, when the terminals 12 and 14 of the fuse 10 are inserted in the terminal receptacles 76 and 78, the bridge 16 slides into the slots 72 and 74. This protects the electrical conducting portion of the fuse; In addition, a person is prevented from accidentally touching the fuse after it is inserted into the protective slots 72 and 74.

In the modification of FIG. 5, the terminal blocks, for example 52 and 54, are held in an interconnecting relationship by inserting a fuse 10 into the appropriate receptacles, for example 60 and 62. Thus the fuse 10 performs two functions: (1) electrical conduction and (2) structural interconnection.

FIG. 6 illustrates an alternative terminal block construction. The terminal block 80 is molded to receive a pair of lead wires 82 and 84 which are appropriately connected to terminal connectors (not shown) within the block 80. The prongs 12 and 14 of the fuse 10 fit into receptacles in the block 80 and electrically connect the wires 82 and 84. The terminal block 80 is constructed of a plastic insulating material such as polypropylene or nylon, though nylon is preferred.

Block 80 has a pair of flexible arms 86 and 88 with catches 90 and 92 which mate with the sides 94 and 96 of modular mounting case 98. Modular mounting case 98 is likewise constructed of an insulating material such as plastic. A snap-on cover plate 100 is attached to the modular mounting case '98 to protect the fuse 10 and prevent harmful contact with the fuse. The cover 100 is constructed of a clear material such as plastic to provide for visual inspection of the fuse 10.

FIG. 7 illustrates the modular mounting case 98 of FIG. 6 mated with the terminal block 80 by means of the arms 86 and 88. The fuse 10 is, of course, inserted in the modular well 102 of the modular case 98. The fuse 10 connects the wires 82 and 84 as shown in FIG. 7. Additional terminal blocks which are fused may be inserted in additional wells such as the well 104 in FIG. 7.

FIG. 8 illustrates an alternative construction of the fuse of the invention. The fuse 20 is comprised of an integrally molded or cast U shaped support member 22 connecting first and second terminals 24 and 26 and a bridge or fuse member 28 also connecting the first and second terminals 24 and 26. The terminals 24 and 26 and the bridge 28 are simultaneously, completely plated at a desired uniform thickness with a low melting fuse metal such as the tin-lead alloy previously disclosed. The body support member or handle 22 gives the fuse construction structural strength as well as providing a means for removing the fuse from a live circuit without contacting the current carrying terminals 24 and 26 or the bridge 28.

The fuse of FIG. 8 may be inserted into a standard fuse clip board 30. Fuse clips 32 and 34 are adapted to receive the terminals 24 and 26 respectively.

While in the foregoing there has been disclosed a preferred embodiment of the present invention, it is to be understood that embodiments obvious to those skilled in the art as well as embodiments which are equivalent are to be included within the scope of the claimed subject matter.

What is claimed is:

1. An electrical fuse comprising, in combination, a fuse body member formed from an electrically nonconductive material and having two electrically conductive terminal prong portions, a rigid, non-conducting, strut member portion interconnecting said prongs and a separate, bridge fuse portion also interconnecting said prong portions, said bridge fuse portion having a cross sectional area no greater than the cross sectional area of either of said prong portions, said prong portions and said bridge fuse portion having a substantially uniform coating of an electrically conductive material; said coating on said bridge fuse portion completely plating said bridge portion; said coating on said bridge fuse portion being a thickness which melts to break a fused circuit when current overload causes excess heating.

2. The combination of claim 1 wherein said fuse body member is a U-shaped rod having a first and second prong, said prongs having equal, constant diameters, said bridge fuse portion connecting said first and second prongs and being cylindrically shaped.

3. The combination of claim 1 including electrical connector means adapted to engage said prongs in an electrical circuit.

4. The combination of claim 3 wherein said electrical connector means comprise a terminal block with an electrically conductive receptacle therein, one of said receptacles being coupled with each of said prongs, said terminal blocks being held in substantially immovable and interlocking relationship by said fuse body member.

5. The combination of claim 3 wherein said electrical connector means comprise terminal blocks mounted by mounting means in predetermined spaced relation, said terminal blocks including electrically conductive receptacles therein, said receptacles being interconnected in pairs by said fuse.

6. The combination of. claim 1 including a single block having first and second receptacles for receiving said first and said second prongs of said fuse to complete an electrical circuit.

7. The combination as set forth in claim 4 including References Cited UNITED STATES PATENTS 3,361,884 1/1968 Parkes 337297 3,268,692 8/1966 Oldham 337201 3,227,841 1/1966 Gaia 337-255 2,955,178 10/1960 Lander et al. 337201 2,941,059 6/1960 Sims et al 337187 2,894,099 7/1959 Cabell 337267 G. HARRIS, Primary Examiner D. M. MORGAN, Assistant Examiner U.S. Cl. X.R. 

